The use of fiber reinforced/resin matrix composite materials, such as graphite fiber reinforced epoxy resin materials, in the fabrication of aircraft components is becoming increasingly important. The fabrication of a component often begins with a roll of composite material consisting of reinforcing fibers preimpregnated with resin and attached to a backing paper. The fibers are oriented in various manners. The most common fiber orientations are a unidirectional orientation of substantially continuous fibers and woven patterns of substantially continuous fibers. An aircraft component is typically fabricated from a plurality of plies having differing shapes and fiber orientations, which plies are formed into a contoured laminate.
The fabrication of such contoured laminates was initially carried out by manual procedures. Such procedures are highly labor intensive and time consuming and, thus, very expensive. In addition, since manual procedures tend to be operator dependent, it is difficult to consistently produce componenets within design tolerances using manual procedures. Therefore, various automated systems for producing contoured laminates have been proposed. The proposed systems generally involve a plurality of steps, including cutting out the plies, separating the plies from scrap and from each other, locating and orienting the plies to lay-up mold surfaces, removing the backing material from the plies, laminating and compacting each ply, and forming the stack of plies to a contour shape. The order of the steps varies from system to system. Preferably, the ply shapes are nested or grouped on the sheets of composite material in order to optimize utilization of the composite material.
There are a number of problems associated with the automated systems which are currently being proposed and/or built for the aerospace industry. The systems generally require complex and costly equipment to separate the cut plies from scrap and from each other. Additional equipment is required to maintain ply accountability (keep track of the plies) throughout the system and to determine ply orientation prior to placing each ply on a lay-up surface. Removing the backing paper from the composite material after the ply cutting process, which usually cuts both the composite material and the backing material, has also required complex equipment. The need for complex and expensive equipment to carry out the various steps of such systems makes such systems very costly. In addition, the large amount of equipment results in very high floor space requirements, which further increase the overall system cost.
U.S. Pat. No. 3,996,089, granted Dec. 7, 1976, to E. R. More et al., discloses a method for handling composite materials. In the method, composite material in tape form is sandwiched between sheets of material called "liners". The composite material tape is more adherent to the lower liner than the upper liner. The tape and liners are positioned on a cutting table with the lower liner adjacent to the table. A vacuum in the cutting table holds the tape and liners in place, and a reciprocating cutter head cuts out a plurality of plies of desired sizes, shapes, and filament orientations. The upper liner and the composite material tape are cut, but the lower liner is left substantially intact. Following the cutting operation, the cut portions of the upper liner are manually stripped off the tape. More et al. state that the stripping of the upper liner can be accomplished by an automated process, but do not describe such a process. With the lower liner still being held to the table by the vacuum, a stacking head sequentially picks up the cut plies. The head moves in position and descends to contact each ply to pick it up. The ply separates from the lower liner because the force of adhesion between the lower liner and the ply is less than the force of the vacuum and the adhesion between the ply and the stacking head (or the ply that was last picked up by the stacking head). The stack of plies is manually removed from the stacking head. More et al. do not show or describe tensioning of either liner or the composite material tape. It appears that a length of tape and a length of each liner material are laid on the table and are substantially coextensive with the table.
Systems in which a sheet-like workpiece is adhered to and is carried by a strip of backing material and in which a portion of the workpiece is separated from the backing material by bending the backing material and workpiece relative to each other are disclosed in U.S. Pat. Nos. 3,574,026, granted Apr. 6, 1971, to L. Kucheck; No. 3,738,888, granted June 12, 1973, to E. C. Williams; No. 4,306,928, granted Dec. 22, 1981, to T. Okui; and No. 4,557,783, granted Dec. 10, 1985, to R. J. Grone et al. In the Kucheck process, label-forming material is temporarily separated from its backing strip by bending the backing strip away from the material. The labels are cut from the separated material and are relaminated onto the backing strip. The remaining skeleton of label-forming material bends away from the labels and is taken up on a separate reel. Between the delamination and relamination steps, the label-forming material is held to a moving belt adhesive side out by a suction device. In the Williams device, resist disks for semiconductive wafers are carried by a backing tape that is held taut yet free to move between a clamping station and a stripping station.
U.S. Pat. No. 3,598,006, granted Aug. 10, 1971, to H. J. Gerber et al., discloses a method in which a stack of sheet material, such as fabric, is held by a vacuum in position to be cut. U.S. Pat. No. 3,615,094, granted Oct. 26, 1971, to G. P. Connor, discloses a method of making an inlay puzzle in which a plastic sheet holds the pieces together during manufacture and is later peeled off by the user. U.S. Pat. No. 3,909,342, granted Sept. 30, 1975, to G. D. Shook, discloses apparatus for making a blanket for laminating on a vessel hull. Scrim material is bonded to a balsa panel, and the panel is cut into squares while still held together by the scrim.
The above patents and the prior art that is discussed and/or cited therein should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.